1. Field of the Invention
The present invention relates to an image display device which makes use of the emission of electrons into a vacuum defined between a face substrate and a back substrate, and more particularly to the structure of a support body which holds and fixes a given gap between both substrates.
2. Description of the Related Art
A color cathode ray tube has been popularly used conventionally as an excellent display device which exhibits high brightness and high definition. However, along with the realization of high image quality of recent information processing device and television broadcasting, there has been a strong demand for a planar display (panel display) which can realize a light-weighted and thin display while ensuring the excellent properties such as high brightness and high definition.
As typical examples of such a planar display device, a liquid crystal display device, a plasma display device and the like have been put into practice. Further, particularly, with respect to the planar display device which can realize the high brightness, various types of panel display devices including an image display device which makes use of emission of electrons into a vacuum from electron sources (hereinafter referred to as “an electron emission type display device” or “a field emission type display device”, hereinafter also referred to as “FED”) and an organic EL display which is characterized by low power consumption are expected to be put into practice in near future.
Among these panel-type display devices, with respect to the electron emission type display device, the display device which has the electron emission structure proposed by C. A. Spindt, a display device which has the metal-insulator-metal (MIM) type electron emission structure, a display device which has the electron emission structure making use of an electron emission phenomenon based on a quantum tunneling effect (also referred to as surface conductive type electron sources), and a display device which makes use of an electron emission phenomenon which a diamond film, a graphite film and carbon nanotubes possess have been known.
Further, among these panel type display devices, the field emission type image display device is configured such that a back substrate which forms cathode lines having field emission type electron sources, control electrodes and the like on an inner surface thereof, and a face substrate which forms an anode and phosphors on an inner surface thereof which faces the back substrate in an opposed manner are laminated to each other by inserting a support frame between inner peripheral portions of both substrates and are hermetically sealed to form a panel, and a sealed space of the panel is held at a pressure lower than an external atmospheric pressure or in a vacuum state.
The above-mentioned control electrodes are arranged in a state that the control electrodes intersect the cathode lines by way of an insulation layer or with an insulation gap therebetween.
Further, in the above-mentioned control electrode, a single or a plurality of apertures which allow electrons from the electron sources formed on the cathode lines to pass therethrough are formed for every pixel. Further, to hold a distance between the back substrate and the face substrate to a distance of a given value, space holding members are interposed between the back substrate and the face substrate. Here, the distance holding members are formed of a thin plate made of glass or ceramics, for example, and are mounted in an erected manner at positions which avoid the pixel.
FIG. 10 is a cross-sectional view of an essential part for explaining the constitution of an image display device which constitutes this kind of conventional panel type display device. The image display device is constituted of a back substrate 2 which mounts a plurality of electron emission elements 5 on a surface thereof, a face substrate 1 which is arranged to face the back substrate 2 in an opposed manner and, at the same time, mounts image forming members 6 on which images are formed due to the irradiation of electron beams emitted from the electron emission elements 5, a frame-like support frame 3 which is interposed between the back substrate 2 and the face substrate 1 and supports peripheral portions of the back substrate 2 and the face substrate 1, and spacers (distance holding members) 4 which are arranged as support columns between the face substrate 1 and the back substrate 2.
In the image display device having such a constitution, as shown in FIG. 11 which is an enlarged cross-sectional view of the essential part, between the peripheral portions of the face substrate 1 and the back substrate 2 which face each other in an opposed manner, the support frame 3 which is formed by assembling glass members having an approximately rectangular cross section into a frame shape has both end surfaces thereof adhered to the face substrate 1 and the back substrate 2 using a sealing material such as a frit glass material, for example, thus adhering and fixing the support frame 3 to the face substrate 1 and the back substrate 2. Further, in the inside of the peripheral portion, the spacers 4 which are formed of a glass member are adhered and fixed to the face substrate 1 and the back substrate 2 while interposing a fixing material made of frit glass or the like, for example (frit glass) between the spacers and both end surfaces. Due to such a constitution, the atmospheric pressure resistance strength and the impact resistance property can be enhanced. This type of image display device is disclosed in Japanese Patent No. 3241219 (Japanese Patent Laid-open Hei 7(1995)-230776 (patent document 1)) or the like.